The present invention relates to apparatus for cutting running webs of paper or the like. More particularly, the invention relates to improvements in cutting apparatus of the type wherein a first rotary knife is movable sideways (namely, transversely of its axis of rotation) and axially toward and away from a second rotary knife.
German Auslegeschriften Nos. 1,024,341 and 1,156,635 disclose sheet cutting apparatus wherein a first knife, which is freely rotatable on its shaft, is movable sideways toward and away from a driven rotary counterknife. Once the first knife reaches a position wherein its marginal portion overlies the marginal portion of the counterknife, the first knife is moved axially so that the two marginal portions contact each other and the counterknife transmits torque to the first knife. The apparatus which are disclosed in the aforementioned publications further comprise means for changing the angular position of an elongated guide member which carries the first knife so that the inclination or orientation of the first knife with respect to the counterknife can be adjusted within a certain range. The means for normally holding the guide member against changes in angular position comprises a spring which is mounted in the guide member and extends into a slide bearing wherein the guide member is movable axially to shift the first knife sideways toward or away from the counterknife. The extent of angular play of the guide member with respect to the slide bearing must be minimal in order to insure that the inclination of the first knife with reference to the counterknife does not change while the cutting apparatus is in actual use. On the other hand, a certain amount of play must exist in order to enable the guide member to move the first knife sideways, i.e., to insure that the means for moving the guide member axially need not apply a pronounced force. It has been found that the wear upon the aforementioned spring and/or slide bearing is extensive, i.e., the extent of angular play of the guide increases gradually and often reaches a value at which the inclination of the first knife with respect to the counterknife is excessive.
The slide bearing is held in the selected position by screws which must be loosened in order to allow for changes in angular position of the slide bearing and guide member for the first knife. To this end, the screws extend into elongated slots of the slide bearing. The adjustment is time-consuming and unreliable because, when the screws are tightened again, some shifting of the slide bearing invariably occurs with the result that the final (adjusted) position of the slide bearing (and hence the inclination of the first knife with respect to the counterknife) deviates from the desired optimum position. Moreover, tightening of the screws entails at least some deformation of the material which is engaged by the heads of the screws, and this often suffices to prevent predictable adjustments of inclination of the first knife.